1. Field of the Invention
The present invention relates generally to a digital interface, and more particularly to an apparatus and method of transferring a transmission stream in a digital interface.
2. Description of the Related Art
In the existing analog type audio/video (A/V) appliance, there exists no method for controlling other peripheral devices through one device. Recently, it becomes possible as digital type A/V appliances are developed.
For instance, in a high-definition digital video cassette recorder (HD-DVCR) conference, an audio/video control command and transaction set (AV/C CTS) is defined so that a remote controller can transmit an operation command to a controlled device, which is called a local device, through an IEEE 1394 serial bus.
Here, the IEEE 1394 serial bus is the standard of a high-speed data transmission defined by Institute of Electrical and Electronics Engineers (IEEE), and is used as an interface which connects respective devices of a digital multimedia system.
The IEEE 1394 serial bus is composed of an isochronous transfer mode and an asynchronous transfer mode. The isochronous transfer mode is used for transmitting A/V data in real time, and the asynchronous transfer mode is used for asynchronously transferring transactions such as read, write, lock and so forth required for the asynchronous transfer mode communication.
Control commands such as the AV/C CTS are asynchronously transmitted using the asynchronous transfer mode.
Meanwhile, according to specifications of consumer-user digital VCRs using 6.3 mm magnetic tapes-PART 8:ATV, specifications of consumer-user digital VCRs and specifications of digital interface for consumer electronic A/V equipment-PART 1, PART 4, it is prescribed that the HDVCR using a 6.3 mm magnetic tape as a recording medium can record a moving picture experts group 2-transport stream (MPEG2-TS) type ATV broadcast transmitted using the IEEE 1394.
Especially, according to the above literature, it is prescribed that the MPEG2-TS is transmitted using the isochronous transfer mode of the IEEE 1394 with a common format in the same manner as a digital video cassette (DVC)(alias camcoder), i.e., a common isochronous packet (CIP) header structure, and the AV/C CTS is adopted as a control command.
Here, the MPEG2 is represented as three standards, MPEG2-system, MPEG2-video, and MPEG2-audio, and as the transmission standard defined in the MPEG2-system exist a transmission stream (TS) and a program stream (PS).
A program is composed of video information, audio information, and user data information, and according to the MPEG2-TS defined in the MPEG2-system, the video, audio, and user data information, which correspond to a plurality of programs, are time-divided and multiplexed in a stream.
The MPEG2-TS includes a program specific information (PSI) so that the audio, video, and user data information corresponding to a desired program are properly analyzed when the MPEG2-TS is demultiplexed in the receiving part.
The PSI has the form of a table in most cases, and a program allocation table (PAT), program map table (PMT), and conditional access table (CAT) exist as representative tables.
The most important tables are the PAT and the PMT among them. The PMT exists for each program, and is a table wherein packet identifications (PIDs) for transmission stream packets including a video stream and an audio stream of a corresponding program are arranged in items. The video stream is represented as PID=XXXX, and the audio stream as PID=YYYY.
The packet of the transmission stream has a fixed length of 188 bytes, and since a plurality of programs generally exist in a transmission stream (TS), a plurality of PMTs exist in a transmission stream (TS).
Accordingly, a general table for connecting a plurality of programs transmitted in the transmission stream to the PIDs for the PMT of the respective program is required, and this general program is just the PAT.
Since one program is represented by one program number, the items of the PAT mostly correspond to information representing the program number=XXXX and the relation to the PMT PID.
Hereinafter, the conventional apparatus and method of transferring a transmission stream in a digital interface will be explained with reference to the accompanying drawings.
FIGS. 1a and 1b are views illustrating the syntax and structure of the PAT used in the conventional IEEE 1394 serial bus.
In the MPEG2-TS currently used in the broadcasts, the PAT information, as shown in FIGS. 1a and 1b, should be necessarily used to decode the stream. Also, between the appliances using the digital interface such as the IEEE 1394 should be necessarily exchanged the PAT information in case of storing or reproducing the MPEG2-TS.
The conventional method of transferring the PAT information is classified into following three methods: a first method of transferring all the PAT information that one source data has, a second method of transferring the program number of the program currently transmitted using a command set of the IEEE 1394, and a third method of modifying the PAT information itself in the source side that transfers the PAT information, and transferring the modified PAT information.
According to the first method, however, since all the PAT information in one source is transferred without modification, a problem may occur when a multi-program is transferred. Specifically, in case that a specified program is reproduced after only the specified program among the transferred multi-program is recorded by a user, the reproducing apparatus may judge that the multi-program exists since the PAT information has all the information on the multi-program, and thus a malfunction may occur during reproduction.